A switched-inductor power converter is the most widely used DC-DC power converter topology in power electronics due to its high efficiency and power-handling ability. A Buck DC-DC power converter can be used to step down voltage from its input/supply to its output/load, and thus are also referred to as step-down converters. An inductor is used in a Buck converter to store energy and two switches are used to control the currents flowing in the inductors.
It is desirable for DC-DC power converters to work at high voltages (e.g., greater than 20 volts (V), high power density, and high frequencies (e.g., greater than 10 megahertz (MHz)), while also providing efficient power delivery and fast transient response. The switches for DC-DC power converters are typically silicon (Si)-based devices, such as CMOS devices for low voltage (e.g., less than 5V) and discrete Si-trench devices for higher voltage (up to 50V). However, Si devices have high on-resistance (Ron) and gate capacitance (Cg), which make it challenging to achieve high switching frequency and high power density. At the same time, low frequency requires larger passive devices (e.g., inductors), thereby necessitating a larger converter size and slower transient response.
High-electron-mobility-transistors (HEMTs), such as GaN transistors, have high breakdown voltage, low on-resistance, and high operation temperature, which makes them ideal candidates to replace Si devices as the switches for high power, high voltage Buck converters. Meanwhile, on-chip magnetic inductors (closed yoke inductors or solenoidal inductors) can provide the dense energy storage required for integrated power converters to achieve the high level integration for high efficiency power delivery and fast transient response.
Currently, the GaN transistor-based power converters use discrete parts, such as a GaN switch chip, a Si CMOS chip and discrete inductors, which are then assembled on a printed circuit Board. This non-integrated structure has a large size, large parasitics, limited switching frequency, and low efficiency.
Thus, DC-DC power converter designs with fully integrated components would be desirable.